*{
	margin:0;
	padding:0;
	box-sizing: border-box;
	font: bold 14px Arial, sans-serif;
	text-align: center;
}
#calculator{
	margin-left: auto;
	margin-right:auto;
	margin-top:100px;
	width:325px;
	height: 240px;
	padding: 20px 20px 9px;
	background: rgb(140,206,236);
}

span{
	border-radius: 5px;
}
.top span.clear {
	background: rgb(252,151,159);
	float:left;
	width:66px;
	height:36px;
	cursor:pointer;
	line-height: 36px;
}

.keys span{
	float:left;
	width:66px;
	height:36px;
	border:1px solid green;
	margin-right: 2px;
	margin-bottom: 2px;
	line-height: 36px;
	cursor:pointer;
}

.keys-num{
	background: rgb(255,255,255) ;

}

.eval{
	background:rgb(241,255,146) 
}
.operator{
	margin-right:0;
	background: rgb(229,213,245);
}
.top{
	height:36px;
	margin-bottom: 4px;
	width: 270px;
}

.top .screen{
	color:white;
	width:198px;
	height:36px;
	border:1px solid blue;
	float:right;
}

